Circuit breaker



April 1930. H. MlLLlKEN I 1,756,374

CIRCUIT BREAKER Filed Feb. 13, 1928 3 Sheets-Sheet 2 INVENTOR HUMPHREYS.MILLIKEN BY G ATTORNE s H. MILLIKEN CIRCUIT BREAKER pril 29, 1930.

3 Sheets-$heet 3 Filed Feb. 13, 1928 FIG. 7

INVENTOR- HUM PHREYS.MILLIKEN ATTORNEYS Patented Apr. 29, 1930 'UNITED STARS @IBGUIT BREAKER Application filed. February 18, 1928. Serial No. 254,052.

This invention relates to new and useful improvements in air circuit breakers, switches, and the like, and particularly to switches used for interrupting large currents at high voltages.

The object of the invention is to provide means for preventing arcs from coming in contact with parts of o posite polarity or grounded structures, an

1 for quickly extinguishing the arc and preventing damage to the switch.

A further. object is to provide a source of I compressed air (or other gas) for extinguishing the arc, which source may be increased so as to increase the current-rupturing capacity of the switch to any desired extent without change in the switch proper.

The switch is herein shown having 3 poles for a 3-phase circuit. The switch may have any number of poles. Each pole has a blade which is provided with a main contact designed to carry the normal current continuously without overheating. Each blade is also provided with a shunt contact forming a shunt path around the main contact. In the opening movement the shunt contact does not open until after the main contact opens. The current is therefore broken by the shunt contact andnot by the main contact. The main contact is thus saved from burning, and its currentcarrying capacity remains unimpaired. a I

The shunt contact is so arranged'that it is surrounded by a blast of air which makes it impossible for the current to extend to the opening blade without breaking through the blast of air, since the fixed contact is inside of the air blast. In the drawingwhich illustrates my invention Figure 1 is a plan view of a switch for three phase current built according to my' invention.

Figure 2 is a side elevation of the switch shown in Figure 1.

Figure 3 is an enlarged part sectional end view of the switch shown in Figure 1.

Figure 4 is a side elevation of an air blast so nozzle cover.

to provide means.

contacts 29 and 30 and ma Figure 5 is an end elevation of the cover shown in Figure 4.

Figure Gisa plan view of the cover.

Figure 7 is an enlarged end view of the spring connection between the section covers to ensure proper working of same.

Referring more particularly to the drawings in which for illustrative purposes I have shown a three pole switch deslgned for a three phase circuit, the switch is shown in its closed position. When the switch is opened the three blades 11 rotate with their centre supports 12 simultaneously in a right hand direction to the open position shown in dotted lines and designated 12% Each of the blades 11 is shown as a centrally clamped bar secured to a four tier mushroom insulator 13, secured at its base to a spindle 14 rotatably mounted in a bearing 13 secured to the frame-member 16.- The lower end of each of the spindles extends below the frame. The central spindle is'provided with a rocker arm 17. The end spindles have each secured to their lower ends levers 18. Connecting rods 19 are pivotally secured to the levers and to the rocker arm so that on movement of said arm,,all of the spindles and the blades will move in unison. Another crank 20 fast to center spindle 14 is connected by the slotted link 21 to the free end of a piston rod 22, which is operated by a pistonworking in a cylinder 23 secured by any suitable means (not shown) to the frame members 24: and 25. Air or such like fluid is fed to the cylinder 23 fromthe storage cylinder 26. The free ends 27 and 28 of the blades 11 press between the e electrical contact therewith. The contacts are secured to an internally threaded tube 31 fitting over the endsof'insulating tubes 32 which areeo secured to the framing members y means of the brackets 33. Mushroom shaped insulators 34 are placed between the brackets and the tubes 31. The insulating tubes 32' extend below the frame and are connected to the air 95 storage tanks 37 by means of connecting pipes 35 and elbows. 36. Three tanks 37 are shown connected together by the pipes 38 and one of said tanks is connected to a source of air supply by a pipe 39. The lower end of each 100 53 is mounted in a cylinder 56 secured to theof the tubes 32 is closed and is provided with a small drain hole 40. Secured to the contact support 31 are the nozzles 41, which have a central rod contact 41 formed integral with ribs 41 secured to the nozzles 41. These con tacts 41 project above, the nozzle and supports. Frictionally engaging with said contacts are the horns 42 secured to the blades 11. The bore of the nozzles 41 surrounds the lower ends of the contacts or terminals 41, to allow air released from the storage tanks 37 to completely surround the said auxiliary contacts 41 To prevent water, snow, or ice, from filling the insulated tubes covers are provided at their up er end. A detail of the covers is shown in igures 4 to 7 inclusive. These covers are made in sections 43 and 44 attached to the supports 41 by the hinge pins 45. The inner edges46 ofthe covers contact with the surface of the contacts 41 and are held in their normally closed position by means of the coil springs 46 surrounding the hinge pins, with their free ends contacting with the said supports 41 and the covers, to exert closing pressure on the cover sections. Positioned in lugs 47 are the fiat springs 48 and spring latches 49, which engage with the lower edges of the spring 48. There is a latch at one side of each cover and a flat spring at the other side, so that the cover'sections will open in unison. Check valves 49 and 50 are mounted in the air supply line 39 which feeds the tanks 37 and 26, to prevent the air from returning to the supply line. A ressure relief valve 51 is secured to one of the tanks 37, so that it will open in case of abnormal rise in temperature and pressure in any of the storage tanks 37 due to sunlight. The switch is held in the closed position against the action of a compression spring 53 by means of a latch 54, which engages with a pin 55 on arm 17. The compression spring frame, and presses against a piston 57secured to the end of a rod 58 connected by a link 59 to a pin 60 on adjacent arm 18. A solenoid 61 operates the latch 54 so that it engages and disengages with the pin 55. A solenoid 66 is connected to one end of alever 62 which is pivotally mounted in a bearing 63 positioned between a spring operated inlet valve 64 and a discharge valve 65. The discharge valve allows the air in the cylinder 23 to flow into the atmos here. The operation of the solenoid is such t at when the one valve is closed, the other is opened. When the piston in the cylinder 23 reaches the end of its outward stroke, a trip latch 67 is operated, this latch being connected to a switch 68 to deenergize the solenoid 66, returning thus the valves to their normal position, that is, with the valve to the atmosphere open and the feed valve closed. A compression spring 69 is mounted in the cylinder 23 to return the piston tothe beginning of its stroke. A valve 70 is mounted in each' of the pipes 35 and is operated by a solenoid 70 When said valves are opened, the air from the storage tanks flows upwardly around the shunt contacts 41*.

The operation of the mechanism is as follows :Air is fed into all storage tanks from the main feed line and the check valve maintains an even pressure-in said tanks and prevents any back fiow of air into the feed line. To close the switch, air is admitted to the cylinder 23 by operating the solenoid 66 in proximity thereto, which closes the exhaust valve and opens the inlet valve. The piston moves forwardly and closes all phases of the circuit simultaneously. The latch 54 is also operated, so that when the circuit is closed, the latch is in pin engaging position holding the switch against the action of the compression spring 53. When the switch is in the closed position and the piston at the outer end of its stroke, the solenoid 66 operating the inletvalve is de-energized and closes the inletvalve, at the same time opening the exhaust valve. The spring'in the cylinder then returns the piston to the end nearest the inlet,

- this return motion being permitted by the slot in link 21. To open the switch, the latch 54 is lifted and the compression spring operat ing at the end of the links turns the blades,

11 to dotted line position, Fig. 1, tobreak the circuit. The slot in link 21 permits the switch to open quickly without moving parts 21 or 22. Simultaneously with the lifting of the latch, to open the switch, the six solenoid operated valves controlling the flow of air from the storage tanks to the tubular supports 32 are opened. The air flows upwardly through the tubes and completely surrounds/the shunt contacts 41 which contact with the horns after the blades are clear of their main contacts.

At the instant the shuntcontacts separate,

the current, if it is very great, jumps across the short air space starting an are which is composed of heated air and metal vapor and probably some ionized air, all of which has a lower resistance than normal air and tends to maintain the current; without a blast of air this arc would grow rapidly to a large volume, and come in contact with parts of the switch of opposite polarity, thus establishing a short circuit and, in the extreme case, causing great damage and failing to perform its function.

With the air blast, however, before the arc can grow, the air blast, being already turned on, drives the low resistance vapors upward, far away from all parts, and replaces the space between contacts by cool fresh air which has such high resistance that the current is reduced to zero. Even in case the current to be interrupted may be so great as to form a large volume of are vapor, the arc is blown instantly to a great height and confined to a definite direction, so that it Will not come in contact with any structure and will therefore cause no damage, and the switch will succeed in interrupting the current.

If the shunt contact. (41) were not surrounded on all sides by the blast of air, it would be possible, in extreme cases, for the arc voltage to cause the arc to jump around the air blast and fail to be extinguished. Hence the importance of arranging the shunt contact within the air blast.

The power which compresses the air is not derived from the switch mechanism and therefore the quantity and pressure of the stored air may be increased to any desired extent without increasing the size of the.

switch parts and without reducing the speed of opening of the switch.

The switch is shown with a main contact and a shunt contact. 'It is quite possible, however, to omit the main contact and allow the shunt contact to become the main and only contact, in which case it would have to carry the normal current continuously without overheating and would be made of suitable dimensions.

By providing covers over the ends of the tubular supports, ice or snow is prevented from collecting therein and interfering with the proper working of the switch. The covers are opened by the air pressing against the underside of same. The auxiliary contacts 41, as shown inFigs. 5 and 6, may be placed nearer one side than the other of the air opening so that the maximum amount of air is directed towards the points between which the spark occurs.

In accordance with the provisions 6f the patent statutes, I have herein described the principle of operation of my invention, together with the apparatus which I now consider to represent the best embodiments thereof, but I desire. to have it understood that the apparatus disclosed is only illustrative and that the invention can be carried out by other means. Also, while it is designed to use the various features and elements in the combinations and relations described, some of these may be altered and others omitted and some of the features of each modification may be embodied in the others without interfering with the more general results outlined, and the invention extends to such use. For instance, it is obvious that the mechanism for operating the switch-blades may be varied indefinitely, as that mechanism cuts no figure in the present invention, and it will also be obvious that the mechanism for operating the blast-valves may be varied indefinitely without departing from the invention.

Having thus described my invention, what I claim is 1. In a circuit breaker, a blade normally held between main contacts, hollow supports for said contacts, auxiliilary contacts positioned centrally of the ho ow supports, horns horns to a minimum as the circuit secured to the blade to frictionally engage ports to completely surround the auxiliary contacts to prevent burning of same when the circuit through the horns is broken. I

2. In a circuit breaker, blades normally held between contacts, hollow supports therefor, auxiliary contacts mounted within the hollow supports, horns secured to the blades and adapted to frictionally engage with the auxiliary contacts when the blades are pulled clear of their contacts, and means to supply air under pressure to completely surround the auxiliary contacts to prevent burning thereof as the horns break circuit therewith.

3. In a circuit breaker, blades normally held between main contacts which are secured to hollow supports, auxiliary contacts in said supports, horns secured tov the blades and adapted to complete the circuit therethrough by engaging with the auxiliary contacts when the blades are clear of their contacts, means for supplying air under pressure through the supports to surround the auxiliary contacts when the horns are bein pulled clear of the auxiliary contacts, and uid operated means for closing the main circuit.

4. In a circuit breaker, blades adapted to complete a circuit through main contacts, tubular supports for said main contacts,

auxiliary contactsmounted in said supports,

horns secured to the blade and adapted to complete the circuit through the blades and the auxiliary contacts when said blades are pulled clear of the main contacts, means to supply air under pressure through said supports to completely surround the auxiliary contacts to reduce to a minimum arcing between them and the horns, and means for closing the hollow supports at one end to protect same against the weather.

5. In a circuit breaker, blades adapted to complete a circuit through main contacts, hollow insulating supports for said contacts, mechanical means for holding the blades in circuit closing position against the action of a compression spring, means for releasing said holding means to break the circuit through the blades and the main contacts, auxiliary contacts within the hollow supports, horns secured to the blades and adapted to frictionally engage with the auxiliary contacts when the circuit through the main contacts is broken, means for supplying air under pressure to surround the auxiliary contacts and reduce the arcing between them and the therethrough is being broken.

6. In a circuit breaker, blades adapted to and engaging with the auxiliary contacts to complete the circuit when the blades are drawn clear of the main contacts, means to supply air under pressure'to surround the auxiliary contacts to reduce arcing to a miniat the upper end thereof, a pair of contacts, one of w ich is supported on said nozzle in position to be surrounded by the blast of fluid as it passes through said nozzle, and a source of fluid pressure connected to the lower end of said insulating tube.

In witness whereof, I have hereunto set my hand.

. 25 sure connected to said nozzle, and means for HUMPHREYS MILLIKEN. 'mum between the horns and the auxiliary contacts as the circuit therethrough is being broken, fluid operated means for moving the bars into engagement with the main contacts.

7. A circuit breaker according to claim 6 having means for closing the'ends of the supports to protect same against the weather, said means. being spring controlled and surrounding the auxiliary contacts and opened by the pressure of air through said supports. 8. In a circuit breaker, a pair of contacts and means for separating them to break the circuit, a nozzle in which one of said contacts is mounted and from the exit-end of which it projects, a source of gas under presreleasing said gas into said nozzle at the instant of separation to produce a blast of gas to thereby prevent arcing.

9. In a circuit breaker embodying a pair of contacts and means for separating them to break the circuit, an. upwardly-directed nozzle in which the upright member of said contacts is mounted, said upright member projecting to a point above the nozzle, a source of gas under pressure connected to said nozzle, and means whereby when the contacts separate a blast of gas will be directed upwardly through said nozzle to thereby surround the contact supported therein at 4 the moment of separation, for the purpose set forth.

10. In a circuit breaker, a pair of contacts and means for separating them to break the circuit, a fluid-conducting nozzle, a source of fluid under pressure connected to said nozzle, and means for releasing said fluid into said, nozzle at the instant of separation to pro-' duce a fluid blast, the afiesaidnozzle being so related to the contacts as to cause the blast of fluid to completely surround the contacts at the point of contact, so that any arc that may form or tend to form when the contacts are separated will be completely enveloped by the ra idly-moving fluid.

11. In a circuit reaker, a pair of contacts and means for separating them, a tubular support for the stationary one of said contacts, this tubular support forming a blast nozzle and being arranged to direct the blast 60 around both contacts at the point of contact,

and means for directing the blast of fluid into said tubularsupport at the moment of separation of the contacts.

12. In a circuit breaker, a tubular support embodying an insulating tube and a. nozzle 

